1. Field of the Invention
The present invention relates to a hand-held type 4-cycle engine used as a power source mainly for a trimmer and other portable working machines, and particularly to an improvement in a system for lubricating a valve-operating mechanism in an engine including a head cover coupled to an upper end of a cylinder head, a valve-operating chamber defined between the cylinder head and the head cover for accommodation of a valve-operating mechanism, an oil mist transfer means for transferring an oil mist produced in an oil tank, an oil recovery chamber for recovering the oil accumulated in the valve-operating chamber by suction, a breather chamber into which a blow-by gas is introduced from the valve-operating chamber and from which the blow-by gas is discharged to the outside, the oil mist transfer means, the oil recovery chamber and the breather chamber leading to the valve-operating chamber, and an oil return passage connected to the oil recovery chamber for returning the oil recovered in the oil recovery chamber to the oil tank.
2. Description of the Related Art
A conventional valve-operating mechanism lubricating system in an engine is already known, for example, as disclosed in Japanese Patent Application Laid-open No. 11-125107.
In the conventional valve-operating mechanism lubricating system in the engine, the oil mist transfer means is connected directly to the valve-operating chamber, so that oil drops generated during transferring of the oil mist are also supplied to the valve-operating chamber and act as a resistance against the operation of the valve-operating mechanism, which is one factor of a power loss.
To enhance the gas-liquid separating function of the breather chamber, it is effective that the volume of the breather chamber is increased. However, to increase the volume of the breather chamber in a conventional breather device, it is necessary to increase the size of the head cover itself. This brings about an increase in size of the engine.
Accordingly, it is an object of the present invention to provide a system for lubricating a valve-operating mechanism in an engine, wherein the valve-operating mechanism can be lubricated without a resistance by supplying an oil mist containing no oil drops to a valve-operating chamber, and the gas-liquid separating function can be enhanced without an increase in size of a head cover.
To achieve the above object, according to a first feature of the present invention, there is provided a system for lubricating a valve-operating mechanism in an engine including a head cover coupled to an upper end of a cylinder head, a valve-operating chamber defined between the cylinder head and the head cover for accommodation of a valve-operating mechanism, an oil mist transfer means for transferring an oil mist produced in an oil tank, an oil recovery chamber for recovering the oil accumulated in the valve-operating chamber by suction, a breather chamber into which a blow-by gas is introduced from the valve-operating chamber and from which the blow-by gas is discharged to the outside, the oil mist transfer means, the oil recovery chamber and the breather chamber leading to the valve-operating chamber, and an oil return passage connected to the oil recovery chamber for returning the oil recovered in the oil recovery chamber to the oil tank, wherein a gas-liquid separating chamber is disposed in the valve-operating chamber below the breather chamber and incorporated in a path extending from the oil mist transfer means via the valve-operating chamber to the breather chamber for separating oil drops from the oil mist or the blow-by gas.
The valve-operating chamber and the oil mist transfer means correspond to a second valve-operating chamber 21b and a one-way valve 61 in each of embodiments of the present invention respectively, which will be described hereinafter.
With the first feature, the gas-liquid separating chamber can be disposed by effectively utilizing a relatively wide space in the valve-operating chamber below the breather chamber. When the gas-liquid separating chamber is provided in a path between the oil mist transfer means and the valve-operating chamber, the oil drops produced during transfer of the oil mist can be separated in the gas-liquid separating chamber, and the oil mist containing no oil drops can be supplied to the valve operating chamber. Therefore, the valve-operating mechanism can be lubricated without a resistance, and a decrease in power loss can be achieved. When the gas-liquid separating chamber is provided in a path between the valve-operating chamber and the breather chamber, the blow-by gas in the valve-operating chamber can be effectively subjected to the gas-liquid separation conducted by two stages of expansion in the gas-liquid separating chamber and the breather chamber, and the blow-by gas containing substantially no oil can be discharged to the outside. Therefore, the unnecessary consumption of the oil can be suppressed. Moreover, since the gas-liquid separating chamber is disposed in the valve-operating chamber below the breather chamber, the volume of the breather chamber within the head cover need not be increased, whereby an increase in size of the head cover can be avoided.
According to a second feature of the present invention, in addition to the first feature, a partitioning member is mounted to an inner wall of the head cover to define the breather chamber between the partitioning member and a ceiling surface of the head cover; the oil recovery chamber is formed integrally with the partitioning member; and the gas-liquid separating chamber is defined between the partitioning member and the cylinder head.
With the second feature, the oil recovery chamber and the breather chamber can be provided in the head cover without dividing a ceiling wall of the head cover. Moreover, both the breather chamber and the oil recovery chamber exist within the head cover and hence, even if the leakage of a small amount of the oil from both of the chambers occurs, the leaked oil is merely returned to the valve-operating chamber without any trouble. Thus, the examination of an oil-tightness around both the chambers is not required and hence, a reduction in manufacture cost can be provided. Moreover, the partitioning member is also utilized to define the gas-liquid separating chamber and hence, the structure can be simplified.
According to a third feature of the present invention, in addition to the first or second feature, the gas-liquid separating chamber is provided between the oil mist transfer means and the valve-operating chamber for separating oil drops from the oil mist fed from the oil mist transfer means to guide the oil mist containing no oil drops to the valve-operating chamber.
With the third feature, the oil drops produced during transfer of the oil mist are separated in the gas-liquid separating chamber, and the oil mist containing no oil drops can be supplied to the valve-operating chamber. Therefore, the valve-operating mechanism can be lubricated without a resistance, and a decrease in power loss can be achieved.
According to a fourth feature of the present invention, in addition to the third feature, the gas-liquid separating chamber is disposed between a pair of intake and exhaust rocker shafts of the valve-operating mechanism which are arranged in parallel to each other.
With the fourth feature, a relatively narrow space in the head cover can be also utilized efficiently to define the gas-liquid separating chamber, whereby an increase in size of the head can be avoided.
According to a fifth feature of the present invention, in addition to the third or fourth feature, the gas-liquid separating chamber communicates with an oil return passage to return the oil drops separated in the gas-liquid separating chamber to the oil tank.
With the fifth feature, the oil drops separated in the gas-liquid separating chamber can be immediately returned to the oil tank, whereby the entering of the oil drops into the valve-operating chamber can be inhibited.
According to a sixth feature of the present invention, in addition to the first or second feature, the gas-liquid separating chamber communicates with the valve-operating chamber and the breather chamber through first and second communication bores, respectively.
With the sixth feature, the blow-by gas in the valve-operating chamber can be subjected effectively to the gas-liquid separation conducted by two stages of expansion in the gas-liquid separating chamber and the breather chamber, and the blow-by gas containing substantially no oil can be discharged to the outside. Therefore, the unnecessary consumption of the oil can be suppressed. Moreover, since the gas-liquid separating chamber is disposed in the valve-operating chamber below the breather chamber, the volume of the breather chamber within the head cover need not be increased, whereby an increase in size of the head cover can be avoided.
According to a seventh feature of the present invention, in addition to the sixth feature, the gas-liquid separating chamber is disposed between components of the valve-operating mechanism.
The components of the valve-operating mechanism correspond to rocker shafts 31i and 31e in each of embodiments of the present invention which will be described hereinafter.
With the seventh feature, a dead space between the components of the valve-operating mechanism can be utilized effectively for disposition of the gas-liquid separating chamber.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.